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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

Regional changes in muscle mass following 17 weeks of bed rest

This work reports on the muscle loss and recovery after 17 wk of continuous bed rest and 8 wk of reambulation in eight normal male volunteers. Muscle changes were assessed by urinary levels of 3-methylhistidine (3-MeH), nitrogen balance, dual-photon absorptiometry (DPA), magnetic resonance imaging (MRI), and isokinetic muscle performance. The total body lean tissue loss during bed rest calculated from nitrogen balance was 3.9 +/- 2.1 kg. Although the total loss is minimal, DPA scans showed that nearly all of the lean tissue loss occurred in the lower limbs. Similarly, MRI muscle volume measurements showed greater percent loss in the limbs relative to the back muscles. MRI, DPA, and nitrogen balance suggest that muscle atrophy continued throughout bed rest with rapid recovery after reambulaton. Isokinetic muscle strength decreased significantly in the thigh and calf with no loss in the arms and with rapid recovery during reambulation.

Leblanc, Adrian D.↗
NASA NTRS1995

Electrical impedance measurements in the arm and the leg during a thirty day bed rest study

The need to detect, follow, and understand the effects of gravity on body fluid distribution is a constant stimulus to the quest for new techniques in this area of research. One of these techniques is electrical bioimpedance spectroscopy (BIS). Although not new, this is a technique whose applications to biomedical research are fairly recent. What is new is the development of instrumentation that has made practical the use of impedance spectroscopy in the biomedical setting, particularly in studies involving human subjects. The purpose of this paper is to report impedance spectroscopy observations made on a subject who was submitted to bed rest for a period of thirty days. These observations were made as part of a study on muscle atrophy during a thirty day head down bed rest. Since bed rest studies are very costly in human and financial terms, and technically difficult to realize, we felt that even though the present study deals only with a single case it was worthy of reporting because it illustrates kinds of questions impedance spectroscopy may help to answer in microgravity research.

Cardus, David↗
NASA NTRS1958

Effect of Rest Periods on Fatigue of High-Purity Aluminum

The effect of rest periods on the fatigue life of high-purity aluminum was investigated under two conditions. In one the specimens were tested at elevated temperatures and the rest periods were given at room temperature; in the second the specimens were tested at room temperature and the rest periods were given at elevated temperature. The results obtained indicated that the increase of life was negligible in the first condition, but an increase of life may be obtained in the second. In order to check this increase in fatigue life a second series of tests has been carried out on a different lot of specimens and again an increase in life was found. This increase of life appeared to be from 30 to 60 percent from the average of the results of 20 tests for each test condition.

Berry, J. W.↗
NASA NTRS1999

Leucocytosis, Thrombocytosis, and Plasma Osmolality During Rest and Exercise: A Hypothesis

The mechanism for inducing leucocytosis (increase in white blood cells) and thrombocytosis (increase in platelets) during exercise is unclear. Because plasma osmolality (Osm) may influence T-cell proliferation, Osm and the number of leucocytes (WBC) and platelets in blood were measured periodically during a 90 min rest period, and were compared with those during upright sitting ergometer exercise in six unt.rained, healthy men who cycled for 70 min at 71% of their maximal oxygen uptake (V prime O(sub 2(sub max)). There were 6 experiments in which the subjects drank different fluid formula-t4ilons (10 ml/kg) of various ionic and osmotic concentrations intermittently during 60 min of the rest period and during the exercise period. Osmolality, and WBC and platelet counts increased significantly (p<0.05) within the first 10 min of exercise, but the additional 60 min of exercise did not significantly change the leucocytosis or thrombocytosis. There were low but significant correlations between individual values of total WBC and total Osm during exercise (r(sub 0.001(2),284) = 0.39) and during rest plus exercise (r(sub 0.001(2),499) = 0.43). With combined data from the six experiments, mean Osm correlated highly and significantly with both mean WBC (r(sub 0.001(2),6) = 0.95, p < 0.001) and mean platelets (r(sub 0.001(2),6) = 0.94, p < 0.01) during the exercise phase. These data indicate that increases in leucocytes, thrombocytes, and osmolality occur primarily within the first 10 min of high-intensity exercise, but neither hypovolemia nor hyperthermia during exercise contributed to the leucocytosis, thrombocytosis, or hyperosmolality. The high correlations between plasma Osm and WBC or platelet counts suggest changes in osmolality may contribute to the mechanism of leucocytosis and thrombocytosis induced by exercise.

McKenzie, M. A.↗
NASA NTRS2000

Differences in Acceleration Training and Exercise Training on Resting Cardiovascular Variables

The relative effects of alternating exercise vs. acclamation training an mean blood pressure (BP, Finapres), cardiac output (CO, BoMed) and peripheral resistance (PR, calculated) were evaluated. Six healthy men (33$\pm$(SD)6 yr. 178$\pm$4 cm, 86$\pm$6 kg) underwent exercise training (ET, n=3): supine on a cycle ergometer (40 to 90\% Vo$_{2}$ max) during exposure to constant+1G$_{z}$ for $\sim$30 min/day for 14 days on NASA's 1.9m Human Powered Centrifuge (HPC). They also underwent oscillatory (between +1 G$ {z}$and$\sim$2.5G$_{z}$) acceleration training (AT, n=3) for $\sim$30 min/day for 14 days on the HPC. After four weeks of ambulatory deconditioning, training protocols were switched. AT increased resting CO by 9.MpmS(SE)3.2\% (p$less than$0.05) with no effect on BF, and ET decreased BP by 9.2$\pm$4.6\% (p$less than$0.08) as well as spectral power of PR by 41$\pm$9\% (p$less than$0.05). The major effect of acceleration training was to increase resting cardiac output while that of exercise mining was to decrease resting blood pressure.

Evans, J. M.↗
NASA NTRS2000

Crew Factors in Flight Operations XII: A Survey of Sleep Quantity and Quality in On-Board Crew Rest Facilities

Many aircraft operated on long-haul commercial airline flights are equipped with on-board crew rest facilities, or bunks, to allow crewmembers to rest during the flight. The primary objectives of this study were to gather data on how the bunks were used, the quantity and quality of sleep obtained by flight crewmembers in the facilities, and the factors that affected their sleep. A retrospective survey comprising 54 questions of varied format addressed demographics, home sleep habits, and bunk sleep habits. Crewmembers from three airlines with long-haul fleets carrying augmented crews consisting of B747-100/200, B747-400, and MD-11 aircraft equipped with bunks returned a total of 1404 completed surveys (a 37% response rate). Crewmembers from the three carriers were comparable demographically, although one carrier had older, more experienced flight crewmembers. Each group, on average, rated themselves as "good" or "very good" sleepers at home, and all groups obtained about the same average amount of sleep each night. Most were able to sleep in the bunks, and about two thirds indicated that these rest opportunities benefited their subsequent flight deck alertness and performance. Comfort, environment, and physiology (e.g., being ready for sleep) were identified as factors that most promoted sleep. Factors cited as interfering with sleep included random noise, thoughts, heat, and the need to use the bathroom. These factors, in turn, suggest potential improvements to bunk facilities and their use. Ratings of the three aircraft types suggested differences among facilities. Bunks in the MD-11 were rated significantly better than either of the B747 types, and the B747-400 bunks received better ratings than did the older, B747-100/200 facilities.

Rosekind, Mark R.↗
NASA NTRS2002

Airline Chair-rest Deconditioning: Induction of Immobilization Thromboemboli?

Air passenger miles will likely double by year 2020. The altered and restrictive environment in an airliner cabin can influence hematological homeostasis in passengers and crew. Flight-related deep various thromboemboli (DVT) have been associated with at least 577 deaths on 42 of 120 airlines from 1977 to 1984 (25 deaths/million departures), whereas many such cases go unreported. However, there are four major factors that could influence formation of possible flight-induced DVT: sleeping accomodations (via sitting immobilization), travelers' medical history (via tissue injury), cabin environmental factors (via lower partial pressure of oxygen and lower relative humidity), and the more encompassing chair-rest deconditioning (C-RD) syndrome. There is ample evidence that recent injury and surgery (especially in deconditioned hospitalized patients) facilitate thrombophlebitis and formation of DVT that may be exacerbated by the immobilization of prolonged air travel. In the healthy flying population immobilization factors associated with prolonged (> 5 hr) C-RID such as total body dehydration, hypovolemia and increased blood viscosity, and reduced various blood flow (pooling) in the legs may facilitate formation of DVT. However, data from at least four case-controlled epidemiological studies did not confirm a direct causative relationship between air travel and DART, but factors such as history of vascular thromboemboli, various insufficiency, chronic heart failure, obesity, immobile standing position, more than 3 pregnancies, infectious disease, long-distance travel, muscular trauma and violent physical effort were significantly more frequent in DVT patients than in controls. Thus, there is no clear, direct evidence yet that prolonged sitting in airliner seats, or prolonged experimental chair-rest- or bed- rest-deconditioning treatments cause deep various thromboemboli in healthy people.

Greenleaf, J. E.↗
NASA NTRS2002

The effect of exercise and rest duration on the generation of venous gas bubbles at altitude

BACKGROUND: Decompression, as occurs with aviators and astronauts undergoing high altitude operations or with deep-sea divers returning to surface, can cause gas bubbles to form within the organism. Pressure changes to evoke bubble formation in vivo during depressurization are several orders of magnitude less than those required for gas phase formation in vitro in quiescent liquids. Preformed micronuclei acting as "seeds" have been proposed, dating back to the 1940's. These tissue gas micronuclei have been attributed to a minute gas phase located in hydrophobic cavities, surfactant-stabilized microbubbles, or arising from musculoskeletal activity. The lifetimes of these micronuclei have been presumed to be from a few minutes to several weeks. HYPOTHESIS: The greatest incidence of venous gas emboli (VGE) will be detected by precordial Doppler ultrasound with depressurization immediately following lower extremity exercise, with progressively reduced levels of VGE observed as the interval from exercise to depressurization lengthens. METHODS: In a blinded cross-over design, 20 individuals (15 men, 5 women) at sea level exercised by performing knee-bend squats (150 knee flexes over 10 min, 235-kcal x h(-1)) either at the beginning, middle, or end of a 2-h chair-rest period without an oxygen prebreathe. Seated subjects were then depressurized to 6.2 psia (6,706 m or 22,000 ft altitude equivalent) for 120 min with no exercise performed at altitude. RESULTS: Of the 20 subjects with VGE in the pulmonary artery, 10 demonstrated a greater incidence of bubbles with exercise performed just prior to depressurization, compared with decreasing bubble grades and incidence as the interval of rest increased prior to depressurization. No decompression illness was reported. CONCLUSIONS: There is a significant increase in decompression-induced bubble formation at 6.2 psia when lower extremity exercise is performed just prior to depressurization as compared with longer rest intervals. Analysis indicated that micronuclei half-life is on the order of an hour under these hypobaric conditions.

Controlled Clinical Trial↗
NASA NTRS1996

Effects of three day bed-rest on circulatory, metabolic and hormonal responses to oral glucose load in endurance trained athletes and untrained subjects

Endurance trained long distance runners and untrained individuals underwent three days of bed rest and oral glucose loading. Before and after bed rest, individuals were given glucose tolerance tests, and their heart rates, blood pressure, blood glucose levels, insulin levels, and catecholamine interactions were measured. Results indicated that glucose tolerance is more affected by bed rest-induced deconditioning in untrained individuals than in trained individuals.

NASA Discipline Regulatory Physiology↗
NASA NTRS1996

Use of bed rest and head-down tilt to simulate spaceflight-induce immune system changes

Bed rest, both with and without head-down tilt, has been extensively used as an earth-bound analog to study physiologic effects mimicking those occurring in weightlessness during spaceflight. We have been able to show in six subjects that 4 weeks of head-down tilt bed rest induces a significant decrease in interleukin-2 secretion by PHA-stimulated T lymphocytes. Another study, lasting 113 days, with two subjects showed a decreased interleukin-2 receptor expression in PHA-stimulated peripheral blood mononuclear cells but a decreased interleukin-2 production in one subject only. Under the same conditions, interleukin-1 production was largely increased in both subjects. Several other immune parameters were also analyzed. Increased interleukin-1 production could contribute to bone mineral loss encountered during bed rest and decreased interleukin-2 secretion could play a role in the appearance of infectious diseases often observed during bed red.

NASA Discipline Neuroscience↗
NASA NTRS1992

Effect of leg exercise training on vascular volumes during 30 days of 6 degrees head-down bed rest

Plasma and red cell volumes, body density, and water balance were measured in 19 men (32-42 yr) confined to bed rest (BR). One group (n = 5) had no exercise training (NOE), another near-maximal variable-intensity isotonic exercise for 60 min/day (ITE; n = 7), and the third near-maximal intermittent isokinetic exercise for 60 min/day (IKE; n = 7). Caloric intake was 2,678-2,840 kcal/day; mean body weight (n = 19) decreased by 0.58 +/- 0.35 (SE) kg during BR due to a negative fluid balance (diuresis) on day 1. Mean energy costs for the NOE, and IKE, and ITE regimens were 83 (3.6 +/- 0.2 ml O2.min-1.kg-1), 214 (8.9 +/- 0.5 ml.min-1.kg-1), and 446 kcal/h (18.8 +/- 1.6 ml.min-1.kg-1), respectively. Body densities within groups and mean urine volumes (1,752-1,846 ml/day) between groups were unchanged during BR. Resting changes in plasma volume (ml/kg) after BR were -1.5 +/- 2.3% (NS) in ITE, -14.7 +/- 2.8% (P less than 0.05) in NOE, and -16.8 +/- 2.9% (P less than 0.05) in IKE, and mean water balances during BR were +295, -106, and +169 ml/24 h, respectively. Changes in red cell volume followed changes in plasma volume. The significant chronic decreases in plasma volume in the IKE and NOE groups and its maintenance in the ITE group could not be accounted for by water balance or by responses of the plasma osmotic, protein, vasopressin, or aldosterone concentrations or plasma renin activity. There was close coupling between resting plasma volume and plasma protein and osmotic content.(ABSTRACT TRUNCATED AT 250 WORDS).

NASA Discipline Regulatory Physiology↗
NASA NTRS1990

Bone mineral loss and recovery after 17 weeks of bed rest

The purpose of this work was to determine the rate and extent of bone loss and recovery from long-term disuse and in particular from disuse after exposure to weightlessness. For this purpose, bed rest is used to simulate the reduced stress and strain on the skeleton. This study reports on the bone loss and recovery after 17 weeks of continuous bed rest and 6 months of reambulation in six normal male volunteers. Bone regions measured were the lumbar spine, hip, tibia, forearm, calcaneus, total body, and segmental regions from the total-body scan. The total body, lumbar spine, femoral neck, trochanter, tibia, and calcaneus demonstrated significant loss, p less than 0.05. Expressed as the percentage change from baseline, these were 1.4, 3.9, 3.6, 4.6, 2.2, and 10.4, respectively. Although several areas showed positive slopes during reambulation, only the calcaneus was significant (p less than 0.05), with nearly 100% recovery. Segmental analysis of the total-body scans showed significant loss (p less than 0.05) in the lumbar spine, total spine, pelvis, trunk, and legs. During reambulation, the majority of the regions demonstrated positive slopes, although only the pelvis and trunk were significant (p less than 0.05). Potential redistribution of bone mineral was observed: during bed rest the bone mineral increased in the skull of all subjects. The change in total BMD and calcium from calcium balance were significantly (p less than 0.05) correlated, R = 0.88.

Non-NASA Center↗
NASA NTRS2004

Airline chair-rest deconditioning: induction of immobilisation thromboemboli?

Air passenger miles will likely double by year 2020. The altered and restrictive environment in an airliner cabin can influence haematological homeostasis in passengers and crew. Flight-related deep venous thromboemboli (DVT) have been associated with at least 577 deaths on 42 of 120 airlines from 1977 to 1984 (25 deaths/million departures), whereas many such cases go unreported. However, there are four major factors that could influence formation of possible flight-induced DVT: sleeping accommodations (via sitting immobilisation); travellers' medical history (via tissue injury); cabin environmental factors (via lower partial pressure of oxygen and lower relative humidity); and the more encompassing chair-rest deconditioning (C-RD) syndrome. There is ample evidence that recent injury and surgery (especially in deconditioned hospitalised patients) facilitate thrombophlebitis and formation of DVT that may be exacerbated by the immobilisation of prolonged air travel.In the healthy flying population, immobilisation factors associated with prolonged (>5 hours) C-RD such as total body dehydration, hypovolaemia and increased blood viscosity, and reduced venous blood flow (pooling) in the legs may facilitate formation of DVT. However, data from at least four case-controlled epidemiological studies did not confirm a direct causative relationship between air travel and DVT, but factors such as a history of vascular thromboemboli, venous insufficiency, chronic heart failure, obesity, immobile standing position, more than three pregnancies, infectious disease, long-distance travel, muscular trauma and violent physical effort were significantly more frequent in DVT patients than in controls. Thus, there is no clear, direct evidence yet that prolonged sitting in airliner seats, or prolonged experimental chair-rest or bed-rest deconditioning treatments cause DVT in healthy people.

Review, Tutorial↗
NASA NTRS2007

Assessment of Immune Status, Latent Viral Reactivation and Stress during Long Duration Bed Rest as an Analog for Spaceflight

As logistical access for in-flight space research becomes more limited, the use of ground based spaceflight analogs for life science studies will increase. These studies are particularly important as NASA progresses towards the Lunar and eventually Mars missions outlined in the 2005 Vision for Space Exploration. Countermeasures must be developed to mitigate the clinical risks associated with exploration class space missions. In an effort to coordinate studies across multiple disciplines, NASA has selected 90-day bed rest as the analog of choice, and initiated the Flight Analogs Project to implement research studies with or without the evaluation of countermeasures. Although bed rest is not the analog of choice to evaluate spaceflight-associated immune dysfunction, a standard Immune Assessment was developed for subjects participating in the 90-day bed best studies. The Immune Assessment consists of: leukocyte subset distribution, T cell functional responses, intracellular cytokine production profiles, latent viral reactivation, virus specific T cell levels, virus specific T cell function, stress hormone levels and a behavioral assessment using stress questionnaires. The purpose of the assessment during the initial studies (without countermeasure) is to establish control data against which future studies (with countermeasure) will be evaluated. It is believed that some of the countermeasures planned to be evaluated in future studies, such as exercise, pharmacologic intervention or nutritional supplementation, have the ability to impact immune function. Therefore immunity will likely be monitored during those studies. The data generated during the first three control studies showed that the subjects in general did not display altered peripheral leukocyte subsets, constitutive immune activation, significant latent viral reactivation (EBV, VZV) or altered T cell function. Interestingly, for some subjects the level of constitutively activated T cells (CD8+/CD69+) and virus-specific T cells (CMV and EBV) both decreased during the studies. This likely reflects the isolation of the subjects (from an immunological perspective) and absence of everyday subclinical challenges to the immune system. Cortisol levels (plasma and saliva) did not vary significantly during the studies. This probably reflects a lack of physiological stress during the study and the stress of readaptation to the 1xG environment at R+1. These data demonstrate the absence of significant immune alteration during 90-day bed rest, and establish control data against which future studies (including countermeasures) may be compared.

Crucian, Brian E.↗
NASA NTRS2007

Multi-System Effects of Daily Artificial Gravity Exposures in Humans Deconditioned by Bed Rest

We have begun to explore the utility of intermittent artificial gravity (AG) as a multi-system countermeasure to the untoward health and performance effects of adaptation to decreased gravity during prolonged space flight. The first study in this exploration was jointly designed by an international, multi-disciplinary team of scientists interested in standardizing an approach so that comparable data could be obtained from follow-on studies performed in multiple international locations. Fifteen rigorously screened male volunteers participated in the study after providing written informed consent. All were subjected to 21 days of 6deg head-down-tilt (HDT) bed rest. Eight were treated with daily 1hr AG exposures (2.5g at the feet decreasing to 1.0g at the heart) aboard a short radius (3m) centrifuge, while the other seven served as controls. Multiple observations were made of dependent measures in the bone, muscle, cardiovascular, sensory-motor, immune, and behavioral systems during a 10 day acclimatization period prior to HDT bed rest and again during an 8 day recovery period after the bed rest period. Comparisons between the treatment and control subjects demonstrated salutary effects of the AG exposure on aspects of the muscle and cardiovascular systems, with no untoward effects on the vestibular system, the immune system, or cognitive function. Bone deconditioning was similar between the treatment and control groups, suggesting that the loading provided by this specific AG paradigm was insufficient to protect that system from deconditioning. Future work will be devoted to varying the loading duty cycle and/or coupling the AG loading with exercise to provide maximum physiological protection across all systems. Testing will also be extended to female subjects. The results of this study suggest that intermittent AG could be an effective multi-system countermeasure.

Paloski, William H.↗
NASA NTRS2009

Gender Differences in Baroreflex Sensitivity after Bed Rest

Two potential contributing factors to post-spaceflight orthostatic intolerance are decreases in baroreflex sensitivity (BRS) and sympathetic nervous system response. The purpose of this study was to examine the shape of the BRS curve and sympathetic response to a wide range of blood pressures (BP) before and during 6 head-down bed rest (BR). METHODS: Normal volunteers were tested one day before BR (20M, 1 0F) and near BR days 30 (20M, 10F), 60 (16M, 8F), and 90 (1 0M, 5F). BP was pharmacologically manipulated by 10-min infusions of phenylephrine (PE) and sodium nitroprusside (SNP) at 3 increasing concentrations with a 20-min rest between PE and SNP. Electrocardiogram and continuous finger blood pressure were recorded. A blood sample was drawn at the end of each infusion to measure plasma norepinephrine levels. The spontaneous baroreflex slope (SBS), a measure of BRS, was calculated as the slope of a sequence of 3 or more beats in which the systolic BP (SBP) and following R-R interval (RR) both increased or decreased. The data included saturated responses at the upper but not the lower end of the BP range. Mean response curves were constructed using second-order mixed model analysis. Results are based on term significance in the models. RESULTS RR: RR was lower during BR than pre BR (p<0.001). Pre BR males were modeled by a linear RR response to SBP (p=0.000) while females had a quadratic response which saturated at high SBP (p=0.019). By day 30, both genders were modeled by a linear response; compared to males, females had an attenuated (lower slope) RR response to changes in SBP (p=0.031). SBS: SBS vs SBP analysis showed a lower SBS during BR (p<0.001) when compared to pre BR. Females had a higher SBS than males pre BR (p=0.006). Females exhibited saturating SBS at higher SBP (p=0.016) on day 30, while males were modeled by a linear SBS response to SBP (p=0.035). NE: Females had different NE response to diastolic BP than males pre BR (p=0.035) and on day 30 (p=0.005). CONCLUSION: NE, RR and SBS responses to BP are affected by gender and BR. Not only do gender and BR baseline differences exist, but gender and BR also influence the slope and saturation of the BRS curves. Attenuated and saturating RR and SBS responses, as well as differences in baseline values, may contribute to the higher rates of orthostatic intolerance in women and after bed rest.

Arzeno, Natalia M.↗
NASA NTRS2012

Integrated Resistance and Aerobic Training Maintains Cardiovascular and Skeletal Muscle Fitness During 14 Days of Bed Rest

Background: Known incompatibilities exist between resistance and aerobic training. Of particular importance are findings that concurrent resistance and aerobic training reduces the effectiveness of the resistance training and limits skeletal muscle adaptations (example: Dudley & Djamil, 1985). Numerous unloading studies have documented the effectiveness of resistance training alone for the maintenance of skeletal muscle size and strength. However the practical applications of those studies are limited because long ]duration crew members perform both aerobic and resistance exercise throughout missions/spaceflight. To date, such integrated training on the International Space Station (ISS) has not been fully effective in the maintenance of skeletal muscle function. Purpose: The purpose of this study was to evaluate the efficacy of high intensity concurrent resistance and aerobic training for the maintenance of cardiovascular fitness and skeletal muscle strength, power and endurance over 14 days of strict bed rest. Methods: 9 subjects (8 male and 1 female; 34.5 +/- 8.2 years) underwent 14 days of bed rest with concurrent training. Resistance and aerobic training were integrated as shown in table 1. Days that included 2 exercise sessions had a 4-8 hour rest between exercise bouts. The resistance training consisted of 3 sets of 12 repetitions of squat, heel raise, leg press and hamstring curl exercise. Aerobic exercise consisted of periodized interval training that included 30 sec, 2 min and 4 min intervals alternating by day with continuous aerobic exercise.

Ploutz-Snyder, Lori↗
NASA NTRS2014

Focal Gray Matter Plasticity as a Function of Long Duration Head-down Tilt Bed Rest

Long duration spaceflight (i.e., 22 days or longer) has been associated with changes in sensorimotor systems, resulting in difficulties that astronauts experience with posture control, locomotion, and manual control. The microgravity environment is an important causal factor for spaceflight induced sensorimotor changes. Whether these sensorimotor changes may be related to structural and functional brain changes is yet unknown. However, increased intracranial pressure that by itself has been related to microgravity-induced bodily fluid shifts: [1] has been associated with white matter microstructural damage, [2] Thus, it is possible that spaceflight may affect brain structure and thereby cognitive functioning. Long duration head-down tilt bed rest has been suggested as an exclusionary analog to study microgravity effects on the sensorimotor system, [3] Bed rest mimics microgravity in body unloading and bodily fluid shifts. In consideration of the health and performance of crewmembers both in- and post-flight, we are conducting a prospective longitudinal 70-day bed rest study as an analog to investigate the effects of microgravity on brain structure, and [4] Here we present results of the first eight subjects.

Koppelmans, Vincent↗